/**
 * This jQuery plugin displays pagination links inside the selected elements.
 *
 * @author Gabriel Birke (birke *at* d-scribe *dot* de)
 * @version 1.1
 * @param {int} maxentries Number of entries to paginate
 * @param {Object} opts Several options (see README for documentation)
 * @return {Object} jQuery Object
 */
jQuery.fn.pagination = function(maxentries, opts) {
    opts = jQuery.extend({
                         items_per_page: 10,
                         num_display_entries: 10,
                         current_page: 0,
                         num_edge_entries: 0,
                         link_to: "javascript:void(0)",
                         prev_text: "<",
                         next_text: ">",
                         ellipse_text: "...",
                         prev_show_always: true,
                         next_show_always: true,
                         callback: function() { return false; }
                         }, opts || {});
    
    return this.each(function() {
                     /**
                      * Calculate the maximum number of pages
                      */
                     function numPages() {
                     return Math.ceil(maxentries / opts.items_per_page);
                     }
                     
                     /**
                      * Calculate start and end point of pagination links depending on
                      * current_page and num_display_entries.
                      * @return {Array}
                      */
                     function getInterval() {
                     var ne_half = Math.ceil(opts.num_display_entries / 2);
                     var np = numPages();
                     var upper_limit = np - opts.num_display_entries;
                     var start = current_page > ne_half ? Math.max(Math.min(current_page - ne_half, upper_limit), 0) : 0;
                     var end = current_page > ne_half ? Math.min(current_page + ne_half, np) : Math.min(opts.num_display_entries, np);
                     return [start, end];
                     }
                     
                     /**
                      * This is the event handling function for the pagination links.
                      * @param {int} page_id The new page number
                      */
                     function pageSelected(page_id, evt) {
                     current_page = page_id;
                     drawLinks();
                     var continuePropagation = opts.callback(page_id, panel);
                     if (!continuePropagation) {
                     if (evt.stopPropagation) {
                     evt.stopPropagation();
                     }
                     else {
                     evt.cancelBubble = true;
                     }
                     }
                     return continuePropagation;
                     }
                     
                     /**
                      * This function inserts the pagination links into the container element
                      */
                     function drawLinks() {
                     panel.empty();
                     var interval = getInterval();
                     var np = numPages();
                     // This helper function returns a handler function that calls pageSelected with the right page_id
                     var getClickHandler = function(page_id) {
                     return function(evt) { return pageSelected(page_id, evt); }
                     };
                     // Helper function for generating a single link (or a span tag if it'S the current page)
                     var appendItem = function(page_id, appendopts) {
                     page_id = page_id < 0 ? 0 : (page_id < np ? page_id : np - 1); // Normalize page id to sane value
                     appendopts = jQuery.extend({ text: page_id + 1, classes: "current" }, appendopts || {});
                     if (page_id == current_page) {
                     var lnk = $("<span class='current'>" + (appendopts.text) + "</span>");
                     }
                     else {
                     var lnk = $("<a>" + (appendopts.text) + "</a>")
                     .bind("click", getClickHandler(page_id))
                     .attr('href', opts.link_to.replace(/__id__/, page_id));
                     
                     
                     }
                     if (appendopts.classes) { lnk.removeAttr('class'); lnk.addClass(appendopts.classes); }
                     panel.append(lnk);
                     };
                     // Generate "Previous"-Link
                     if (opts.prev_text && (current_page > 0 || opts.prev_show_always)) {
                     appendItem(current_page - 1, { text: opts.prev_text, classes: "disabled" });
                     }
                     // Generate starting points
                     if (interval[0] > 0 && opts.num_edge_entries > 0) {
                     var end = Math.min(opts.num_edge_entries, interval[0]);
                     for (var i = 0; i < end; i++) {
                     appendItem(i);
                     }
                     if (opts.num_edge_entries < interval[0] && opts.ellipse_text) {
                     jQuery("<span>" + opts.ellipse_text + "</span>").appendTo(panel);
                     }
                     }
                     // Generate interval links
                     for (var i = interval[0]; i < interval[1]; i++) {
                     appendItem(i);
                     }
                     // Generate ending points
                     if (interval[1] < np && opts.num_edge_entries > 0) {
                     if (np - opts.num_edge_entries > interval[1] && opts.ellipse_text) {
                     jQuery("<span>" + opts.ellipse_text + "</span>").appendTo(panel);
                     }
                     var begin = Math.max(np - opts.num_edge_entries, interval[1]);
                     for (var i = begin; i < np; i++) {
                     appendItem(i);
                     }
                     
                     }
                     // Generate "Next"-Link
                     if (opts.next_text && (current_page < np - 1 || opts.next_show_always)) {
                     appendItem(current_page + 1, { text: opts.next_text, classes: "disabled" });
                     }
                     }
                     
                     // Extract current_page from options
                     var current_page = opts.current_page;
                     // Create a sane value for maxentries and items_per_page
                     maxentries = (!maxentries || maxentries < 0) ? 1 : maxentries;
                     opts.items_per_page = (!opts.items_per_page || opts.items_per_page < 0) ? 1 : opts.items_per_page;
                     // Store DOM element for easy access from all inner functions
                     var panel = jQuery(this);
                     // Attach control functions to the DOM element 
                     this.selectPage = function(page_id) { pageSelected(page_id); };
                     this.prevPage = function() {
                     if (current_page > 0) {
                     pageSelected(current_page - 1);
                     return true;
                     }
                     else {
                     return false;
                     }
                     };
                     this.nextPage = function() {
                     if (current_page < numPages() - 1) {
                     pageSelected(current_page + 1);
                     return true;
                     }
                     else {
                     return false;
                     }
                     };
                     // When all initialisation is done, draw the links
                     drawLinks();
                     });
};